Abstract: This specification discloses a rudderless sailing craft with two sails of approximately equal area and a vertical keel affixed to the hull near a balance point between the two sails. The central part of the craft between the two sails serves as an unobstructed cockpit area free of overhead sails and swinging booms. The craft is steered by controlling both sails simultaneously from the cockpit area using a mechanism consisting of either a single rope rigged to both sails or a steering wheel and gearbox with chain-drives which rotate the booms at the base of each sail. For steering, the mechanism differentially alters the trim angle of the two sails causing the force exerted by the wind to increase on one sail and to decrease on the other sail. The hydrodynamic force on the keel acts as a fulcrum about which the differential forces exerted by the sails provide the turning moment necessary for steering the craft. For changing coarse heading or adjusting the angle of heel, the mechanism trims the sails in unison.

Abstract: A log periodic antenna (1) comprising two substantially identical non-resonant elongated log periodic conductive zig zag structures (3,5). The structures (3, 5) lie side-by-side in close proximity to each other in substantially the same plane defined by a planar dielectric board (13). The zig zag structures (3, 5) are axisymmetric about a line of symmetry coinciding with the midline of an impedance matching feed line (18). The feed line (18) comprises two substantially identical elongated conductive members (7, 9), sandwiched around the dielectric (13). The first zig zag structure (3) and the first member (7) lie on one side of the dielectric board (13), while the second zig zag structure (5) and the second member (9) lie on the other side of the board (13). At microwave frequencies, the zig zag structures (3, 5) and the member (7, 9) are preferably mounted on the dielectric board (13) using printed circuit techniques.

Abstract: A compact, low-profile broad-banded log-periodic antenna comprises a planar conductor (3) partially sandwiched by but electrically insulated from two substantially parallel spaced-apart ground planes (4, 8). The sandwich extends as far as an imaginary plane (15) that is orthogonal to conductor (3) and to the ground planes (4, 8). Conductor (3) comprises an alternating series of radiating loops (L(n)) and non-radiating transmission-line loops (L(j)). The non-radiating loops (L(j)'s) lie on the ground plane (4, 8) side of plane (15). The radiating loops (L(n)'s) lie on the other side of plane (15). Optional additional ground planes (6, 10) may be employed, in which case they lie in plane (15) and meet one of the primary ground planes (4 or 8, respectively) along a common edge. The length (d) of the loops (radiating or non-radiating), the spacing (D) between loops, and the height (h) and width (w) of the radiating loops (L(n)) are all scaled by a factor (S) which is less than 1 but greater than 0.

Abstract: A leaky waveguide slotted traveling wave antenna having several elongated nonresonant slots (2) oriented with their long axes substantially orthogonal to the direction of propagation within waveguide (1) filled with a dielectric material having a dielectric constant greater than 1. The length (m) of each slot (2) gradually increases as one traverses the waveguide (1) along the direction of propagation, whereas the width (W) of the wall of the waveguide (1) in which the slots (2) are cut gradually decreases as one traverses the waveguide (1) along the direction of propagation. Any angle of radiation between 0.degree. and 135.degree., including endfire and broadside radiation, can be achieved. The width (w) of each slot (2) and the inter-slot spacing (d) can vary; the increase in slot length (m) can be non-uniform.

Abstract: This specification discloses a nondissipative load termination for a traveling wave antenna array whereby energy incident at the end of the antenna array is applied directly to the main beam of the array with the same polarization as the main beam so that the gain of the antenna is improved.

Abstract: This specification discloses an antenna system with a left antenna array having a pair of radiators and a right antenna array having a pair of radiators. The spacing of the radiators is such that one antenna array produces a positive phase backlobe and the other antenna produces a negative phase backlobe. Appropriate processing of the signals from the two antenna arrays permits exclusion of any signal received in the backlobe of the two arrays. The spacing between the radiators in one array is determined by the equation .lambda.(0.25 +x) and the spacing between radiators in the other array is determined by the equation .lambda.(0.25 -x) wherein .lambda. is the wavelength of an electrical signal applied to the antenna system and x is the radiator spacing differential in wavelengths.